Abstract
This article presented the behavior of ores containing black copper under acid leaching. The solution potential was modified by adding agents, and five leaching conditions were evaluated, one as a control based on sulfuric acid leaching (conventional), and the others by changing the solution potential with: ferrous sulfate (FeSO4), white metal (Cu2S), sulfur dioxide (SO2), and ozone (O3). Leaching behavior was evaluated with laboratory bottle (ISO-pH) and column leaching tests. Two ores samples from the Lomas Bayas mine were used. The samples, identified as low (LG) and high grade (HG), were characterized as 0.13–0.25% Cu and 0.15–0.38% Mn, respectively. The mineralogical analysis indicated that black copper represented around 20% of total Cu (0.05% Cu). The results of the bottle tests indicated that the solution potential decreased with the addition of reducing agents, while the copper extraction rate with the HG sample increased to 83.7%, which exceeded the extraction rate obtained by conventional acid leaching by 25%. Ozone did not favor the extraction of Mn and Cu extraction when the solution potential increased. Cu and Mn extraction were directly related. The results of the column leaching tests showed that it was possible to maintain the solution potential at values below 600 mV (SHE) with the addition of white metal and sulfur dioxide while obtaining the highest copper extraction rate of approximately 60%, which was 18% higher than the rate obtained with conventional leaching. Sulfuric acid consumption was 11 kg/t over 45 days of leaching.
Highlights
The presence of exotic ore bodies is an important characteristic of the porphyritic systems in the central Andes [1,2]
The results of the column leaching tests showed that it was possible to maintain the solution potential at values below 600 mV (SHE) with the addition of white metal and sulfur dioxide while obtaining the highest copper extraction rate of approximately 60%, which was 18% higher than the rate obtained with conventional leaching
Together with green oxides are present the black copper minerals, which are difficult to recognize darkly colored mineraloid compounds with complex mineralogy and polymetallic associations [5]; black copper ores are refractory to acid leaching, with slow dissolution rates in conventional hydrometallurgical systems
Summary
The presence of exotic ore bodies is an important characteristic of the porphyritic systems in the central Andes [1,2]. These exotic deposits vary widely in size, reaching up to 3.5 million tons of fine Cu as copper oxide [3,4]. The Lomas Bayas deposit in northern Chile includes a large area with the presence of exotic copper known as black oxides or black coppers. According to geological and mineralogical studies, 30% of the non-soluble copper in the Lomas Bayas deposit is due to the presence of black copper [6,7].
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